The invention relates to an epitaxial semiconductor layer sequence on a semiconductor substrate for use in the manufacture of infrared-emitting diodes. In particular, the invention relates to an epitaxial semiconductor layer sequence made of GaAlAs mixed crystal.
The manufacture of semiconductor diodes from epitaxial GaAlAs mixed crystals to achieve a higher light yield is known from Gillessen et al, light Emitting Diodes, Prentice/Hall International, (Englewood Cliffs, N.J.) 1987, p. 117 ff. To do so, silicon-doped GaAlAs is grown by the liquid-phase epitaxy method onto an n-doped GaAs semiconductor substrate. The temperature of the liquid is reduced from a high temperature at the start of the epitaxial growth to a lower one. The high temperature has the effect that the silicon initially brings about n-doping of the epitaxial layer. At a critical temperature, the conductivity type of the epitaxial layer changes from n to p. The pn-junction is created. At the same time, the aluminum content in the grown layer is steadily reduced from the substrate to the surface, since the liquid is depleted of aluminum.
The semiconductor substrate is now removed with a stop etchant and the diode provided with contacts, with the surface previously forming the barrier surface to the substrate now being the light-emitting surface. Removal of the substrate is necessary to permit light emission at the exposed GaAlAs surface.
Removal of the substrate is technically very difficult and hence expensive. The thin epitaxy layers left behind are very prone to breaking when being handled for further processing. In addition, the high aluminum content makes it difficult to provide the contacts.
The object underlying the invention is therefore to provide a semiconductor arrangement consisting of GaAlAs on a semiconductor substrate that can be used for the manufacture of infrared-emitting diodes whose substrate layer can be retained during diode manufacture.